Flexural Slip in an Anticlinal Plungeout as a Mechanism for Dike Offsets: Nahal Ardon Valley,Ramon National Geological Park,Israel |
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| Abstract: | This paper investigates the flexural-slip mechanism in a dome-shaped termination of an anticlinal fold. The flexural slip in the area is expressed by regular offsets of dikes at the contact with a sill, and by many small-scale detachment structures in layered strata. The flexural slip structures are localized in two stratigraphic levels, marking two slip horizons. The lower horizon is located at the top of the Triassic sequence, at the contact between the competent Triassic dolostone and the soft Jurassic strata, which are rich in clay. The upper slip horizon is located within the Jurassic strata at the level of a basaltic sill. The interval between the two slip horizons (32 m) is almost undeformed. Kinematic indicators demonstrate that the slip verges toward the center of the dome structure of the Ramon anticline, and coincides with the directions of the dike offsets. The structural observations suggest that beddingplane slip is the result of flexural-slip folding of the Ramon anticline. The directions in which the dikes are shifted depend upon both the orientations of the slip vector and the dike trends. Amounts of flexural slip, reflected in the dike offsets at the contact with the sill, were calculated as a function of strata dips and thickness of the beds between slip horizons. Estimated and measured magnitudes of displacement are in agreement (± 16%) for the 7 observed dikes. |
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